Method of treating fibrous pulp



` Jan. 18, 1944.

G. L. BlDwELl. f 2,339,453

METHOD OF TREATING- FIBROUS PULP i 2 Sheets-Sheet 1 Filed June 26', 1940 INVENTOR I 1.525106 ZZ Jan. 18, 1944. G. l.. BlDwl-:LL

METHOD OF TREATING FIBROUS PULP Filed June 2s. 1940 2r sheets-sheetV 2 y ATToRNEYs Patented Jan. 18, 1944 METHOD 0F TREATING FlBItOUS PULP George L. Bidwell, Riegelsvilla Pa., assignor to Riegel Paper Corporation, New York, N. Y., a corporation o fNew Jersey application June 26, 1940, serial No. 342,455

2 claims. (ci. 21o-199) This invention relates to a method of treating pulp and morel particularly to a method of dewatering pulp. p

In the present invention I provide a method whereby a batch of pulp may be brought to a predetermined consistency. In paper making it is frequently necessary to provide large batches of stock of predetermined consistency. The present practice is to circulate the pulp through a trough, tub or chest which is made very deep to obtain capacity and remove a part of the water from the pulp while itis being circulated.

One method now in use is to employ an octagon shaped washing cylinder that is about one-half submerged in lthe pulp when in operation. Another method is to employ a star shaped washer.l Both of these methods are open to several objections. -Neither of them will dewater the stock sufliciently rapid to make their use practical. The star shaped washer is open to the further objection that it displaces too much stock and reduces the capacity o the trough.

In dewatering ck according tomy method, I employ a round cylinder of relatively small dlameter which is completely submerged in the pulp. The cylinder is provided with a facing of wire netting or other suitable foraminous material. As the stock `circulates in the trough and Y -may be of any suitable size and shape.

through which the pulp is circulated and which The trough is preferably made deep to permit it to handle large batches of stock and it may be made U-shaped as shown, for convenience of assembly or of any other desired shape. The trough is provided with an inlet end 2 and an outlet end 3 forming two legs 4 and 5 connected by section 6.

As shown (see Fig. 2) the bottom of the trough motor I I.

leads to the inlet end of a refining Aengine I3. The

may incline downwardlyjfrom the inlet end 2v to the central section 6 as indicated at 'I and between the outlet 3 and the central section 6, the bottom of the-trough may be inclined downwardly as indicated at '8. The inclined bottom insures thorough circulation of the entire body of the stock, but if desired a. trough of the desired capacity having a horizontally arranged bottom may be used. The outlet end 3 of the trough is connected to a pump 9 'through'a pipe I0 and the circulating pump 9 is driven by a suitable From the pump a discharge pipe I2 refining engine may be of any of the standard types now employed by paper-makers for grinding stock.v As illustrated and as generally constructed, it is formed of a conical shell lined with knives (not shown) in which is arranged a revolving plugr (not shown) carrying knives which the cylinder rotates, the stock forms a mat on the exterior of the cylinder and a portion of the water contained in the stock passes through the facing into the cylinder and thence to a drain.

The stock in slush form (of thin consistency) is pumped from a bleacher or screen chest into the circulating trough. The dewatering cylinder discharges through the wall of the trough into a suitable drain. The stock is circulated from the outlet end of the trough through a refining engine and returned to the inlet end of the trough. The submerged cylinder is 'slowly revolved in the direction of iiow of the stock and a mat formed on the cylinder. The mat so formed is washed oilz as the cylinder passes the top center by the force of the flow of stock traveling toward the outlet.

In the accompanying drawings I have shown one embodiment of the apparatus suitable for use in practicing the process and forming a part of the invention. In this showing:

Fig. 1 is a plan view;

Fig. 2 is a side elevation ;l

Fig. 3 is a transverse,` vertical, section view in line 3-3 of Fig. 1; and

Fig. 4 is a similar view online 4--44 of Fig. 3.

The reference numeral I designa' es a trough cooperate with the knives of the shell to produce a grinding action. The outlet end of the refining engine is connected to the inlet end of the trough by a. pipe I4,

Within the trough and adjacent the outlet end I provide a cylinder I5 of relatively small 'diameter, compared'to the depth of the trough, which is provided with a closed end IB and is open at the other end. The interior of the cylinder communicates with a drain pipe I 'I extending through thewall of the trough and having a. control valve I8 arranged therein. The cylinder is adapted to rotate and may be driven from a motor I9 and by means of a belt 2li. The belt passes over a pulley ZI on the motor shaft and-over a pulley 22 mounted on the shaft 23 of the cylinder. A plurality of spiders 24 are mounted on shaft 23 A and they support a facing 25 which is preferably formed of an inner layer of relatively coarse wire and an outer layer of iinerwire. A collar 26 is arranged on the wall of the trough adjacent the open end of the cylinder and a similar collar 21 is carried by the cylinder and abuts or engages the collar 26. A packing strip 28 surrounds these two collars` and serves to prevent loss of stock.

In operation the pulp in slush form is pumped into the circulating trough. In a specific einbodiment of the invention employing a trough of 3500 pounds capacity, I employa cylinder I5 of 30" diameterand 56" face. The cylinder is revolved at a speed of from 30 to 35 R. P. M. and as the stock is circulated through the trough by the pump Il, it forms a mat on the facing 25 of the cylinder and the water drained from that portion of the stock which forms the mat flows into the cylinder and to drain pipe I1. thickness of the mat formed on the cylinder is controlled by valve I8. Care must be taken not to form too thick a mat or the capacity of the dewatering device will be diminished. The drain pipe I1 is provided with a vent pipe 30 extending to the full height of the trough. As the cylinder I5 slowly revolves, the dewatered pulp is removed Thefrom its face at top center by the'force of the stock flowing toward the outlet end 3 of the trough.

With apparatus of the size and dimensions heretofore described, I have found it possible to bring stock from a 21/2 to 3% consistency to a consistency of i1/2% in twenty minutes total time. This timeis computed from the time when the pulp is first started until the trough is lled with 3500 pounds of 4.5% consistency pulp. The dimensions heretofore given of the speciiic embodiment are of course merely for the purpose of illustration and are not intended to be restrictive. Likewise I have found that the best results are obtained when a coarse wire netting is first arranged on the cylinder and covered with a ner wire screen. For this plu'pose I have employed a #14 backing wire with a #30 facing.

wire.

I claim:

1. The method of dewatering pulp used in the l manufacture of paper to reduce it to a desired consistency which comprises delivering the pulp to be dewatered to a container having an inlet end andoutlet end, iiowing the pulp through the container over a foraminous revolving cylinder arranged between the inlet end and the outlet end, the cylinder being entirely submerged in the pulp whereby a mat is formed on the cylinder and removed therefrom by the iiowng pulp as the cylinder is revolved, withdrawing water from the interior of thecylinder, withdrawing the pulp from the container at the outlet end after the pulp has passed over the cylinder, returning the pulp to the container at the inlet end, and continuing the recirculation of the pulp until it has reached the desired consistency.

2. The method of dewatering pulp used in the manufacture of paper to reduce it to a desired consistency which comprises delivering the pulp to be dewatered to a container having an inlet end and outlet end, flowing the pulp through the container over a. foraminous revolving cylinder arranged between the inlet end and the outlet end, the cylinder being entirely submerged in the pulp whereby a mat is formed on the' cylinder and removed therefrom by the flowing pulp as the cylinder is revolved, withdrawing water from the interior of the cylinder, withdrawing the pulp from the container at the outlet end after the pulp has passed over the cylinder, passing the pulp through a rening engine,- returnin-g the pulp to the container at the inlet end, and recirculating the pulp until it has reached the desired consistency.

GEORGE L. BIDWELL. 

